By Rolling StoneApr 28, 2010 8:36 PM EDTA fter two whirlwind days with Robert Downey Jr. in Los Angeles, Walter Kirn discovers the greatest actor of his generation is a hardass, a flake, a superstar — anything you want him to be. The Up in the Air author profiles the Iron Man 2 superstar in Rolling Stone's new issue, on sale at newsstands today — and available for All Access readers right now.

During an introspective day on the beach where Kirn and Downey play word association (and coin the term "vaginal parfait"), the actor opens up about his opposition to drug legalization, his interest in science and conspiracy and his current state of mind, which he describes as "the continual process of transcending fear-based rituals." During the pair's second afternoon together, Downey gets gritty, speaking out about the downward spiral that led to his ultimate fall: his incarceration from 1999-2000.

Downey recounts how he'd partied with "the son of a local phenom," smoking black-tar heroin on a two-day bender, just before getting busted for driving with drugs and guns in his possession. He returned home from jail and started searching for "that great coke" he knew he'd stashed somewhere in the house.

"And here I was needing to anesthetize like never before. The wife has moved out, the kid's gone, my life is a fucking babyshambles, and I suddenly make the neuropathic connection that there's nowhere the coke can be but the garbage, and I fucking dig in the thing and there it is, and it's so fucking pure and so clean and there I am, in my own kitchen, cooking up some rock — no Vicodin, no Valium, nothing to take the edge off, barely a trace of fucking Absolut Citron left in the fridge, and I just go, 'This is as good as it gets right now.' I just go, 'Bam!,' triumph of the spirit. And the next thing that happens, I'm in custody within two weeks for even stranger reasons, and the phone rings, and it's the phenom's son and he goes, 'Hey, dude, do you have any more of that opium?' I, of course, told him it was opium. Never call it heroin, it's very taboo. But this stuff, this Mexican sludge, just grabbed you by the fucking heartstrings and tore me apart. All those years of snorting coke, and then I accidentally get involved in heroin after smoking crack for the first time. It finally tied my shoelaces together. Smoking dope and smoking coke, you are rendered defenseless. The only way out of that hopeful state is intervention."